Nylons are engineering thermoplastics which are often selected for applications because of favorable balance of properties, e.g. low gas permeability, toughness against impact, resistance to deformation at elevated temperatures, tensile strength, stiffness and chemical resistance. Nylons are routinely used in fabricating articles that can be injection molded. However, because of inherently low melt viscosity at low deformation rates common nylons, e.g. nylon-6, nylon-6,6 and copolymers thereof, are generally considered unsuitable for blow molding and sheet extrusion applications. The melt viscosity at low deformation rates of such common nylons can be increased by chain extension of such nylon, e.g. by vacuum autoclaving, to provide blow moldable and sheet extrusion grades of such common nylons. Alternatively, when nylon properties are desired in blow molded articles other less common, e.g. specialty, nylons can be used. Because of the increased cost of chain extended nylons and specialty nylons many blow molding and sheet extrusion applications for nylons are avoided in favor of other more viscous polymers with a less favorable balance of properties.
An object of this invention is to provide blow moldable nylon resins based on common nylons, e.g. nylon-6, nylon-6,6 and copolymers thereof, which have an inherently low relative viscosity, e.g. about 50.
Another object of this invention is to provide methods of blow molding nylons of inherently low relative viscosity.
Still another object of this invention is to provide blow molded articles comprising nylons of low relative viscosity.
These and other objects which will be apparent from the following disclosure are achieved by blow molding nylon resin blends comprising nylon resin having a relative viscosity of less than about 100 and sufficient melt viscosity enhancing polymer so that the blend is adaptable to be blow molded or sheet extruded over a temperature range of at least about 25.degree. C.